Boolean Problem with not generating new Difference faces
I had created a simple box with an inset and internal "extrusion" with a bevel. Then I duplicated it and "joined" the two boxes. Then continued to have internal hidden surfaces that were overlapping with curves due to bevels. When I attempted to apply a "difference" boolean operation using Bool Tools, it didn't generate the new faces.

I stepped backward and instead did the following:


I create the initial inset and extruded and beveled boxes, and overlapped them like before.
This time I applied a union boolean operation to the two cubes instead of just joining them, which removed the hidden faces
Finally I created the cutter and used bool tools to difference the cutter on the unionized boxes.


It created the faces, but it also applied the earlier boolean union on the boxes at the same time. I was hoping it would be completely non-destructive, but it wasn't. So maybe the lesson is: duplicate and hide shapes that are unioned non-destructively before adding a cutter using a difference boolean, so you can roll back if needed.